Unveiling the Potential of Solar-Powered Multistage Hollow Fiber WGMD: A Transient Performance Evaluation

Area of Science:

• Renewable Energy Engineering
• Water Desalination Technologies
• Computational Fluid Dynamics

Background:

• Freshwater scarcity is a growing global challenge, necessitating sustainable solutions.
• Solar energy offers an abundant, renewable heat source for water desalination.
• Membrane distillation (MD) is a promising desalination technology driven by vapor pressure differences.

Purpose of the Study:

• To develop and validate a computational fluid dynamics (CFD) model for hollow fiber water gap membrane distillation (HF-WGMD) systems integrated with solar collectors.
• To investigate the transient performance of the solar-driven HF-WGMD system under varying solar irradiation.
• To analyze the impact of system parameters, particularly solar collector area and multistage configurations, on desalination efficiency and energy consumption.

Main Methods:

• A 2D axisymmetric CFD model was developed to simulate the HF-WGMD module's performance.
• A lumped-parameter transient flat-plate solar collector (FPC) model was coupled with the CFD framework.
• The integrated model predicted feed water temperature and module flux under time-varying solar irradiation.
• Experimental data was used for model validation.

Main Results:

• Increasing solar collector area from 10 to 50 m² enhanced average water flux by 6.4 times, reaching 10.9 kg/(m²h).
• Module flux strongly correlated with solar intensity, peaking at 18.4 kg/(m²h) with 35 m² collectors.
• Multistage HF-WGMD systems demonstrated significant reductions in specific thermal energy consumption (424 kWh/m³ for a 40-stage system) and improved overall solar desalination efficiency to 57.5%.

Conclusions:

• The developed CFD model accurately predicts the performance of solar-driven HF-WGMD systems.
• Solar collector area is a critical parameter for maximizing water flux in single-stage systems.
• Multistage configurations offer substantial improvements in energy efficiency and freshwater productivity, highlighting the viability and optimization potential of solar-powered desalination.